2017 20.9660714285714
2016 21.1707650273224
2015 21.0005479452055
2014 20.901095890411
2013 20.9865753424658
2012 21.0901639344262
2011 21.0402739726027
2010 21.5712328767123
2009 20.967397260274
2008 20.9093548387097
2007 20.9381578947368
2006 21.0638356164384
2005 21.4005917159763
2004 20.9265671641791
2003 21.0452941176471
2002 20.8904761904762
2001 20.7846153846154